Motion picture film and method of photography



Jan. 21, 1936. Q D EY R 2,028,275

MOTION PICTURE FILM AND METHOD OF PHOTOGRAPHY Filed Sept. 25, 1934 350 400 45c J00 55v 600 6 5a 7a a 750 350 I 4-00 4J0 J00 550 600 65a 700 7-97;

UNITED STATES PATENT OFFICE MOTION PICTURE FILM AND METHOD OF PHOTOGRAPHY Charles B. Dreyer, Los Angeles, Calif., assignor of one-half to Henry F. Boeger, Los Angeles,

Calif.

Application September 25, 1934, Serial No. 745,442

7 Claims.

This invention relates to a method of producing monochromatic cinematographic films which contain images of objects photographed in such relation that an effect of relief, depth, or of unusual definition is obtained. By the method of this invention, for example, certain desired objects or portions of objects being photographed, may be caused to stand out with much greater definiteness than other objects or portions of objects. As a result, the method and means of this invention are particularly applicable to the production of unusual and fantastic effects and to the production of films which appear to have depth or relief.

Generally stated, the method contemplates the simultaneous recording of two images of an object or scene on two emulsions, said emulsions being preferably carried by a single film in spaced relation, the images recorded in one of such 20 emulsions being quite sharp and critical whereas the images recorded in the other emulsion are slightly diffused.

The method also contemplates means whereby the amount of diffusion or definiteness obtained may be readily controlled without the necessity of using special cameras, projectors, or changing the film. The method of this invention permits a portion of the picture area or a portion of the object being photographed to stand out with unusual definiteness, such result being accomplished by changing the character of the illumination used on the object being photoggraphed.

In one form 'of my invention the two emulsions may be placed on opposite sides of a backing strip, such as the normal cellulosic composition backing strip of normal cinematographic films. In another form the two layers of emulsion may be applied to the same side of the backing strip, the emulsions differing from one another in their sensitivity to bands of wave lengths of light. These two layers of emulsion may, if desired, be spaced by a suitable medium provided witha dye adapted to act as a light filter so as to insure the recording of but a particular band of wave lengths of light upon the rear emulsion, or such layers of emulsion may be separated by means of a diffusing translucent layer of material adapted to cause the rear emulsion to record a diffused image. Preferentially, the front emulsion (the emulsion which faces the camera lens and object or scene being photographed) is an emulsion sensitive to a range of wave lengths embracing wave lengths differing more than 259 millimicrons from each other, such front emulsion, however, being insensitive to aband of wave lengths within such range. Means are provided (either by sensitizing the rear emulsion or by the use of a suitable light filter or dye) whereby the rear emul- 5 sion becomes preferentially sensitive and/or preferentially records wave lengths of light to which the front emulsion is substantially insensitive. In other words, the rear emulsion should preferentially record wave lengths to which the 10 front emulsion is substantially insensitive.

As will be described hereinafter in greater detail, the method contemplates the use of emulsions of the character stated and the regulation bf illumination during photography whereby the 15 intensity of images recorded on either front or rear emulsions may be controlled by such variations in illumination characteristics to the effect that when said emulsions are printed upon a single positive stock and projected, high lights or certain portions, objects or parts of the scene originally photographed may be caused to become accentuated or diffused, such accentuation or diffusion being the result of the regulation of illumination during photography.

It is an object of this invention, therefore, to disclose and provide a method of producing monochromatic motion picture film carrying images which give rise to stereoscopic effect when projected. I

Another object is to disclose and provide a method of producing monochromatic motion picture film in which the images exhibit relief, roundness or depth.

A further object is to disclose and provide a method whereby any desired object or portion of an object being photographed may be caused to either stand out or merge with the background photographed by simply changing the character of the illumination used on the object during photography.

These and other objects, uses and advantages, as well as modifications and adaptations of the invention, will become apparent to those skilled in the art from the following detailed description of a preferred method of putting the in,-

vention into operation.

In describing the invention, reference will be had to the appended drawing, in which:

Fig. l is a spectrograph illustrating the sensitivity of a front emulsion to light of different wave lengths.

Fig. 2 is a spectrograph showing the sensitivity of a rear emulsion to light of various wave lengths.

Fig. 3 is a plan view diagrammatically illustrating the arrangement of camera, emulsions and lights with respect to a scene being photographed.

As is well known, the ordinary photographic emulsion is most sensitive to the shorter wave lengths of light, such as the blue and violet. By the use of sensitizers, the range of the emulsion may be extended so that a so-called panchromatic emulsion is sensitive not only to the violet and blue but also to the green and yellow. It is possible, by the treatment of emulsions with certain dyes, to render the emulsions sensitive to a relatively long range of wave lengths, that is, a range in which the difference in wave lengths between shortest and longest wave lengths recorded in the emulsion amounts to 250 .to 400 millimicrons.

Furthermore, by carefully selecting the dyes or other sensitizing agents, it is possible to pro-' duce an emulsion which in addition to being sensitive over the range indicated, will at the same time be substantially insensitive to a band or hands within such range.

For example, a. silver bromide emulsion, when treated with dicyanin in water and alcohol and containing about 0.5% of ammonia, will be sensitive to wave lengths of around 430 millimicrons and also to wave lengths of about 725 millimicrons. Within this range, however, the emulsion will be substantially insensitive to a band between about 525 and 550 millimicrons, this band corresponding to what is known as green.

This invention utilizes the substantial insensitiveness of emulsions to bands of wave lengths within the general range of the emulsion. If, for example, two strips of film are simultaneously exposed photographically to a scene, the front emulsion (facing the lens and object) being a silver bromide emulsion sensitized with dicy anin and described hereinabove, and a light filter similar to the mercury green Wratten filter having a transmission at about 520-545 millimicrons (or a medium carrying a dye adapted to impart a transmission characteristic similar to said mercury green filter) is interposed between such front emulsion and the emulsion carried by the rear film (which rear emulsion can be a standard panchromatic emulsion) and the two strips of film, while in substantial contact, are simultaneously photographically exposed to the scene or object, then the first emulsion will record wave lengths from about 430 to 725 whereas the rear emulsion will only record wave lengths of about 520 to 545. The green portions of the scene will not be recorded upon the front emulsion but they will be recorded upon the rear emulsion. Light filters adapted for use .between the two emulsions and having transmission characteristics of the mercury green mentioned may be made by using 1.25 cc. of acid green J. C. per '7 grams of 12% gelatin solution, or by using a mixture of 1 cc. tartrazine and 1 cc. of naphthol green per 7 grams of such gelatin solution. It is to be understood that, for monochromatic work, the dyes used in the intermediate light filtering layer are preferably of a water-soluble type and capable of being removed by washing during development of the film.

In accordance with this invention, in the event the photographer wishes to cause the image of a person, present in the -scene being photographed, to be accentuated or emphasized upon the photograph, then by illuminating such person. with green light, an image of such person also on the rear emulsion. When during such photography the scene is focused upon the front emulsion and the two emulsionsused are separated slightly, as by a refractive layer (see Patent No. 1,960,373), or by means of a layer of diffusing material, then the image of such person (illuminated in green) will be diffused upon the rear emulsion.

-When the negative, taken as described hereinabove and comprising the two emulsions, is converted into a positive by printing both of such emulsions upon a single positive emulsion, then the resulting positive image will show all portions of the scene clearly, the person who had been illuminated with green light being particularly clear and definite, thereby placing such person into relief. In this manner it is possible to either accentuate or substantially eliminate objects existing in the scene. photographed, during photography. For example, in

' the event it was desired to have the person hereinabove referred to appear and disappear in the projected images of a motion picture taken of such scene, then it is only necessary to gradu upon projection give the effect of a gradual materialization of such person.

In order to more accurately describe the invention, reference will be had to the appended drawing. Fig. 1 illustrates the sensitivity of a silver bromide emulsion treated with dicyanin and containing a small quantity of Pinacyanol blue. This emulsion as shown is sensitive throughout the range of about 375 to 725 millimicrons but is substantially insensitive to a band of light having wave lengths of between 500 and 585. In the event it is not desired to use a light filter between such front emulsion and the rear emulsion (the light filter passing only light of wave length between 500 and 600, for example), then the rear emulsion used may be a negative emulsion treated with Pinachrome. The sensitivity of an emulsion treated with Pinachrome to visible spectra is indicated in Fig. 2. Such back or rear emulsion will be sensitive to light of from about 400 to 650 millimicrons in wave length, thereby being sensitive to that band of light to which the front emulsion is substantially insensitive.

The front and rear emulsions, illustrated in Figs. 1 and 2 respectively, may be mounted upon a suitable carrier, such as the carrier ID, the front emulsion being indicated at I and the rear emulsion indicated at 2. picture camera is indicated at 9 and the scene to be photographed is generally indicated at H, such scene including the two figures l2 and I3. The scene is focused upon the front emulsion I. A layer or film of diffusing material, such as for example starch, rice starch, finely ground solid (such as mica or talc) or other substance, which layer is translucent to light, may be introducedbetween the emulsions l and 2 for the purpose of creating diffusion of the image recorded in the rear emulsion 2. v

A similar diffusion in the rear emulsion may be attained by the use of an intermediate layer of inert positive emulsion, such as one containing an excess of iodide.

Sources of substantially white light are indicated in Fig. 3 at M and I5. In the event the scene were to be photographed with only the The motion sources l4 and I5 supplying illumination, then both of the figures i2 and I3 would appear on the front emulsion. A very faint diffused image of both figures would also appear on the rear emulsion. When it is desired to accentuate the figure i2, then a source of yellow-green light, indicated at I6, is energized, this light being particularlyfdirected upon the figure i2. As a result, a more contrasty image of figure I2 will be developed upon the back or rear emulsion 2. In the event the light sources It and i5 were provided with light filters capable of absorbing all yellow and green light, then as long as the figure i2 was illuminated with both light from source, and light from source I 6, it would record on both front and rear emulsions and therefore be much more distinct, definite and contrasty than the image of figure i3, as the image of figure i3 would.

only register upon the front emulsion.

The illumination used may also be reversed, the entire scene being illuminated with green so as to produce but a faint image upon the front emulsion whereas the light source i6 may be blue, thereby emphasizing the image of figure i2 while retaining the image of figure H3 in a diffused condition. By regulating the intensity of the light from the source I 6, the image of the figure i2 may be caused to become diffused or definite, depending upon the amount of light thrown thereon. In addition, the emulsions may be reversed, that is, the front emulsion may only be sensitive to a relatively narrow band of wave lengths whereas the rear emulsion is sensitive to a relatively wide range but substantially insensitive to a narrow band.

It is further to be understood that although in the embodiment of the invention specifically referred to hereinabove one of said emulsions was substantially insensitive to green, the band of insensitiveness may be shifted either toward the red or toward the violet. The width of such band of relative insensitiveness need not exceed 20 millimicrons. The preparation of emulsions which are sensitized to certain wave lengths but are substantially insensitive to others is well known in the art and no claim is made upon the dyes or other sensitizing agents used, per se.

The band of wave lengths to which one of the emulsions is substantially insensitive, but which band is recorded on the other emulsion employed in accordance with this invention, is preferably positioned in the spectrum between wave lengths of 450and Q50 millimicrons, but need not include this entire 200 millimicron range, as pointed out hereinabove.

Two emulsions which can well be employed in the combination and in the manner stated are the following:

An emulsion known as type U, which has a maximum sensitivity to light of 680-720 millimicrons, is only very slightly sensitive to light of between 520-600 millimicrons, and which is fairly sensitive to light of between 420 and 500 millimicrons, the total range of the emulsion extending from about 400 to 740 millimicrons, and an emulsion known as type H, having a total rangeof about 430-580 millimicro-ns with a maximum sensitivity to light of between 480- 560 millimicrons. These emulsions are made by Eastman Kodak of Rochester, New York. When using these emulsions and when it is desired to increase the intensity of the image recorded on type U in the range of 440 to 500 millimicrons, the subject or object being photographed may be illuminated with light contain ing a high proportion of these wave lengths, as by the use of suitable light filters between the light source and the subject.

Those skilled in the art will readily understand and observe the numerous uses, adaptations and modifications coming within the scope of this invention. The above method and means obviate the difficulties heretofore encountered from the uncontrollable presence and effect of infrared rays, by the selective action of the rear (generally) emulsion. All changes, modifications, adaptations, results and benefits coming within the scope of the appended claims are embraced thereby.

I claim:

1. In monochromatic motion picture photography, the steps of passing light from an object to be photographed through a front emulsion sensitive to a range of wave lengths of light but insensitive to a band of wave lengths within said range, to record an image of said object, and then passing the light transmitted through said front emulsion upon a rear emulsion preferentially sensitive to wave lengths of light including said band to which the front emulsion is not sensitive, and illuminating those portions of the object being photographed which it,.is desired to accentuate with light containing wave lengths to which both emulsions are sensitive while illuminating the remainder of the scene with light composed essentially of wave lengths to which only one of the emulsions is preferentially sensitive.

2. In monochromatic motion picture photography, the steps of focusing an object to be photographed on a front emulsion sensitized to a relatively wide range of wave lengths of light but substantially insensitive to a band of wave lengths within said range, so as to form an image of said object, simultaneously passing the light from said object onto a rear emulsion preferentially sensitive to wave lengths of the band to which the front emulsion is substantially insensitive, so as to simultaneously form two images on the said front and rear emulsions, and illuminating those portions of the object which it is desired to accentuate with light composed substantially of wave lengths within the band to which said front emulsion is insensitive.

3. In monochromatic motion picture photography, the steps of providing a front emulsion sensitized to a range of wave lengths embracing wave lengths differing more than 250 millimicrons but substantially insensitive to a band of wave lengths within said range; providing a rear emulsion adapted to record wave lengths of light to which the front emulsion is substantially insensitive; photographing a scene upon said emulsions to simultaneously form two images on the said emulsions, and illuminating portions of the scene which it is desired to relief or accentuate with light containing wave lengths to which both emulsions are sensitive while illuminating the remainder of the scene with light containing wave lengths to which only one of the emulsions is preferentially sensitive.

4- aoasms spaced from the front emulsion adapted to record wave lengths of light to which the front emulsion is substantially insensitive; said rear emulsion being insensitive to shorter and to longer wave lengths; photographing a scene upon said emulsions to simultaneously form two images on the said emulsions, and illuminating portions of the scene which it is desired to relief or accentuate with light containing wave lengths to which both emulsions are sensitive while illuminating the remainder of the scene with light containing wave lengths to which only one of the emulsions is preferentially sensitive.

5. In monochromatic motion picture photography, the steps of providing a front emuision sensitized to a range of wave lengths embracing wave lengths diflering more than 250 millimicrons but substantially insensitive to a band of wave lengths within said range; providing a rear emulsion upon the same film but spaced from the frontemulsion adapted to record wave lengths of light to which the front emulsion is substantially insensitive; photographing a scene upon said emulsions to simultaneously form two images on the said emulsions, illuminating portions of the scene which it is desired to relief or accentuate with light containing wave lengths to which both emulsions are sensitive while illuminating the remainder of the scene with light containing wave lengths to which only one of the emulsions is preferentially sensitive, developing the images recorded in both emulsions on the film at the same time, and then printing both images upon a single coated positive film.

6. A film for use in monochromatic motion picture photography, comprisng a backing strip provided with two photographic emulsions, one of said emulsions being sensitive to a range of wave lengths embracing wave lengths differing more than 250 millimicrons but being substantially insensitive to a band of wave lengths within said range, the other of said emulsions being adapted to photograpically record wave lengths to which the first emulsion is substantially insensitive.

'7. A film for use in monochromatic motion picture photography, comprising a backing strip provided with two photographic emulsions, one of said emulsions being sensitive to a range of wave lengths embracing wave lengths differing more than 250 millimicrons but being substan tially insensitive to a band of wave lengths within said range, the other of said emulsions beingadapted to photographically record wave lengths to which the first emulsion is substantially insensitive, and a color filter carried bysaid backing strip and positioned between said emulsions, said color filter being adapted to transmit light of wave lengths to which the last mentioned emulsion is sensitive.

CHARLES E. DREYER. 

